- What made the barium platinocyanide screen glow when Röntgen's cathode-ray tube was covered?
Physical Chemistry
The physics underlying chemical structure and reaction.
- What is osmotic pressure and why does a solvent migrate toward whatever is dissolved on the other side of a membrane?
- How did van 't Hoff's laws on chemical equilibria and reaction rates turn physical chemistry into a mathematical discipline?
- What everyday medical technologies depend on a correct understanding of osmosis?
- What are purines, and why did Fischer's work on them turn out to matter for genetics?
- What did Arrhenius's 1884 doctoral thesis claim happens to salts when they dissolve in water?
- Why did Arrhenius's examiners at Uppsala react so poorly to his theory of electrolytic dissociation?
- Which other physical chemists championed Arrhenius's ion theory before it was widely accepted?
- What physical phenomena did the theory of electrolytic dissociation end up explaining?
- How much raw ore did the Curies have to process to isolate just one gram of radium?
- Why did argon go undetected for the entire history of chemistry before 1894?
- What did the noble gases have in common that made them a coherent chemical group rather than isolated curiosities?
- Why was finding an element that doesn't react with anything actually difficult?
- Why did so many chemists die or fall ill trying to isolate fluorine before Henri Moissan succeeded?
- What role did extreme cold and a platinum-iridium cell play in Moissan's successful isolation of fluorine?
- What other invention of Moissan's, besides isolating fluorine, was recognized in his Nobel Prize?
- How did calcium carbonate in a glass column cause different plant compounds to separate into bands?
- What problem had chemists run into with phenol and formaldehyde before Baekeland's work?
- What is catalysis, and why does a catalyst remain unchanged after speeding up a reaction?
- What industrial process did Ostwald develop for producing nitric acid, and what was it used for?
- Why did the Nobel committee award Ostwald for building a discipline rather than for a single discovery?
- Why did hydrogen ion concentration need a logarithmic scale rather than a linear one?
- What does a change of one unit on the pH scale actually represent in terms of acidity?
- How did Wallach's structural work on terpenes end up underpinning the rubber industry?
- How do modern pyrometers use Wien's law to infer a star's or a furnace's temperature from its color?
- How did nitrogen become oxygen in Rutherford's experiment?
- What did the Braggs' method reveal about the atomic arrangement of sodium chloride and diamond?
- What method did Willstätter use to work out the structure of chlorophyll without modern spectroscopy?
- How is chlorophyll's porphyrin ring structurally related to haemoglobin?
- What experimental steps let Willstätter's team identify chlorophyll's porphyrin ring and central magnesium ion using only 1910s chemistry?
- What role did sodium citrate play in making blood storable rather than requiring an immediate donor?
- What was Gilbert Lewis's 1916 proposal about atoms sharing electron pairs, and how did Langmuir build on it in 1919?
- Why did Irving Langmuir win the Nobel Prize in Chemistry in 1932 while Gilbert Lewis, who originated the shared-electron idea, never did?
- How did Stern and Gerlach's setup with silver atoms and a magnetic field test the prediction of discrete orientations?
- How does ultraviolet light convert ergosterol into vitamin D?
- How did Arthur Harden discover that phosphate was essential to fermentation?
- What is haemin and why does it sit at the core of the haemoglobin molecule?
- How are haemoglobin and chlorophyll molecular cousins, and what actually differs between them?
- What structural features make haemin a chemically difficult molecule to synthesize?
- How did Friedrich Bergius apply high-pressure hydrogenation to turn coal into synthetic fuel?
- What did Langmuir discover about how molecules arrange themselves in single layers on a surface?
- Why does surface chemistry behave so differently from the chemistry of a material's interior?
- What practical inventions did Langmuir produce alongside his theoretical work on surfaces?
- How did the Joliot-Curies produce radioactive isotopes that don't occur in nature?
- How did Debye's methods change physical chemistry from a discipline of recipes into one of geometry?
- What are chemoreceptors in the carotid bodies and aortic arch, and how do they sense blood gas levels?
- Why does the carbon-fluorine bond make PTFE so chemically inert and heat-resistant?
- How did Edward Doisy determine the chemical structure of vitamin K after Dam identified its existence?
- What made the structures of alkaloids like morphine and strychnine so difficult for nineteenth-century chemists to determine?
- What is the electronic theory of organic reaction mechanisms that Robinson developed, and why does it still underpin undergraduate chemistry?
- What is a branched chain reaction, and how does it differ from a simple chain reaction?
- Why does a branching ratio determine whether a reaction burns steadily or detonates?
- What practical fields rely on the quantitative theory of branched chain reactions today?
- What chemical bonds did Alexander Todd map out in synthesizing ATP and related coenzymes?
- How does a superheated liquid reveal the path of a charged particle passing through it?
- What pressures and temperatures did making polyethylene require before Ziegler's catalyst discovery?
- Why are polyethylene and polypropylene among the highest-volume manufactured chemicals today?
- What raw material does the body start from when it synthesises cholesterol, and how many enzymatic steps does the full pathway take?
- Why were chemists unable to observe what happens during extremely fast chemical reactions before the 1950s?
- How does Eigen's relaxation method use a disturbance to equilibrium to measure a reaction's speed?
- How did Norrish and Porter use flash photolysis to capture chemical intermediates that vanish in nanoseconds?
- What kinds of biological processes, like photosynthesis, became measurable once these fast-reaction techniques existed?
- What did Derek Barton show about how a molecule's 3D shape affects its chemical reactions?
- What did the Venera probes reveal about the composition and pressure of Venus's atmosphere?
- How does UDP-glucose drive the assembly of glycogen and cellulose inside cells?
- How did the Apollo 13 crew improvise a working carbon dioxide scrubber from mismatched parts?
- What makes free radicals so difficult to study directly in a laboratory?
- How did Herzberg's spectroscopic catalog of free radicals end up shaping atmospheric chemistry and astrophysics?
- Why did the tools that worked well on small molecules fail to describe how long polymer chains behave?
- What is Flory's excluded-volume theory, and what does it explain about a coiled polymer chain in solution?
- What is a 'theta solvent,' and why did the concept become standard vocabulary in polymer science?
- What are frontier molecular orbitals and why do they govern a molecule's reactivity?
- How does Taube's electron-transfer chemistry explain the corrosion of pipes and bridges?
- How does a crossed molecular beam machine let chemists observe a single reaction instead of a bulk average?
- What can the angles and velocities of scattered reaction products reveal about a chemical reaction?
- How did infrared chemiluminescence let John Polanyi study molecules immediately after they formed?
- Why did establishing reaction dynamics as geometry and energy transfer make it possible to design drug molecules rather than stumble on them?
- What temperature record did Bednorz and Müller's copper-oxide ceramic break in 1986?
- What exactly did Pons and Fleischmann claim happened inside their palladium electrode in heavy water?
- Which sugars in beans cause intestinal gas, and why can't the body digest them directly?
- What does Marcus theory predict about the rate of electron transfer between molecules?
- What is the 'inverted region' in electron transfer, and why did chemists initially doubt it?
- How long did it take before experiments confirmed Marcus's predictions?
- What chemical compounds did the Shiseido research team identify as responsible for foot odor?
- Why were carbocations so hard to study before Olah's work, given how common they are in industrial chemistry?
- How do superacids stop a carbocation from reacting away, and why does that let chemists examine it with NMR?
- What industrial processes, like oil cracking or fuel refining, depend on understanding carbocation chemistry?
- How did Murad's finding about nitroglycerin connect to Furchgott's endothelium-derived relaxing factor?
- How did George Goble use liquid oxygen to light a charcoal barbecue in three seconds?
- How much faster was Goble's method compared to a conventional charcoal lighting approach?
- What did astronomers detect in Hale-Bopp's coma for the first time in any comet?
- How can electrons collectively behave as though each one carries only a third of the standard electron charge?
- What extreme conditions of temperature and magnetic field were needed to observe the fractional quantum Hall effect?
- How did Walter Kohn's use of electron density instead of the full wavefunction make molecular calculations tractable?
- What role did John Pople's Gaussian program play in turning density functional theory into a practical laboratory tool?
- How short is a femtosecond, and why did chemists need pulses that brief to observe a reaction?
- What technique did Ahmed Zewail develop to photograph molecules mid-reaction?
- How did femtochemistry change the transition state from a theoretical construct into an observable event?
- Why was one bronze statue in Kanazawa conspicuously free of pigeon droppings?
- What role did arsenic in the statue's alloy play in keeping pigeons away?
- How did Yukio Hirose confirm which compound in the bronze was responsible?
- What process was used to purify the tap water before it was sold as Dasani?
- What role does a metal carbene complex play in Chauvin's proposed mechanism?
- Why did sodium chlorate, used to kill ragwort, make New Zealand farmers' trousers combustible?
- What purpose are these stress-triggered frog odours thought to serve?
- How did Cussler and Gettelfinger raise the viscosity of a swimming pool for their experiment?
- What problem does the word 'the' create for professional indexers?
- How do different library and database systems decide whether to file 'The Beatles' under T or B?
- What did Glenda Browne's paper on the definite article contribute to indexing practice?
- How did the disappearance of white material over four Martian days prove it was water ice rather than dry ice?
- What did Phoenix's discovery of perchlorates in Martian soil complicate about thinking on habitability?
- What property of tequila's ethanol-water ratio makes it suitable for depositing diamond film?
- How does heating vaporized tequila to 800 degrees Celsius produce diamond rather than graphite on a substrate?
- What compound in wasabi did researchers use to design a fire alarm for deaf sleepers?
- How quickly could the airborne wasabi compound wake a sleeping person?
- What industrial applications do nanodiamonds produced this way have?
- Why did residents of Anderslöv who showered frequently notice their hair turning green?
- What chemical reaction between copper ions and shampoo compounds caused the green tint?
- How did Pettersson trace the problem back through the town's plumbing rather than blaming the shampoo?
- What compound does a cut onion release that causes eyes to water, and how does it form sulphuric acid in the eye?
- What is lachrymatory-factor synthase and what did discovering it reveal about the onion's biochemistry?
- Why had the enzyme behind onion tears gone unnoticed for decades despite the tear-inducing compound being known?
- How does STED microscopy use a second laser to sharpen resolution below the diffraction limit?
- What chemical signature suggested the streaks were caused by briny water rather than dry sediment?
- What happens to egg-white proteins during denaturation?
- How does Feringa's molecular motor rotate continuously in one direction using light?
- How much higher were real-world nitrogen oxide emissions compared to the legal limit?
- Why shouldn't liquid water exist at the cold Martian poles, and what could keep it from freezing?
- What chemical signature does a housefly leave behind after briefly touching a glass of wine?
- Where does phosphine come from on Earth, and why does its presence usually imply a continuous source?
- What did Jane Greaves and colleagues detect in the cloud deck of Venus in September 2020?
- Why was the phosphine detection on Venus contested and revised after the initial announcement?
- What compound spiked in cinema air during tense movie scenes?
- How did researchers measure a film's emotional arc through air chemistry alone?
- What chemical property of PTFE (Teflon) makes it pass through the digestive system unaltered?
- What causes a cacio e pepe emulsion to break into a grainy, clumped sauce?
- How does feedback between PIN transporter regulation and auxin-responsive ARF-Aux/IAA signalling drive the switch between passage and spot patterns of auxin distribution?
- What ceramic materials are used in FDM filaments and what applications does each target, such as zirconia for dental use and PZT for piezoelectric devices?